This project is aimed at determining the basis of processes involved in auditory sensory transduction. We have confirmed that the electrically evoked fast contractile response of isolated outer hair cells is membrane potential dependent. Our evidence was based on using externally applied electric field and membrane permeabilizing agents. We are examining a hypothesis that calcium ion is involved in the response as the second messenger. This hypothesis is based on our recent finding of an initial enhancement, followed by an obolishment, of the motile response when we applied a Ca++ permeabilizing agent during the electrical stimulation of OHC. The increase in cytosolic calcium was monitored with fluo-3, a calcium indicator dye. We are studying the subplasma lamina- a two dimensional network of filaments present at the lateral wall of OHC. This subplasma lamina is responsible for the very fast recovery of the cylindrical shape of the cell even after extensive deformation produced by osmotic swelling. We are also testing an exciting new hypothesis in which micropillar structures arranged in parallel arrays between the laminated cisternae and the plasma membrane would mediate the transfer of mechanical energy to stress activated channels during motility activity of OHC. Several studies of basic intracellular transport of organelles are in progress We have demonstrated that brain and adrenal kinesin mediate translocation of purified cromaffin secretary granules along the surface of microtubules. We have also found another unexpected property of kinesin which is to organize microtubules into radial aggregates resembling aster structures in cells.